1. Field of the Invention
The present invention relates to a linear motor which is capable of increasing peak thrust and simultaneously counterbalancing a cogging thrust produced due to an edge effect of an armature, and in which the length of the linear motor in the axial direction can be adequately constructed.
2. Description of the Related Arts
A prior art linear motor is constructed as shown in FIG. 9. In the drawing, the linear motor is composed of a rotor 31, an armature 32 attached to the rotor 31, a fixed portion 38 facing the armature 32 via spacing, permanent magnets 37a, 37b, 37c, . . . attached to the fixed portion 38. The armature 32 is such that an armature winding 36 is accommodated in a winding accommodation groove of an armature core 33 in which an armature iron plate having teeth 34a, 34b, 34c, . . . produced by punching out electromagnetic steel plate like comb teeth and forming a winding accommodation groove 33a, and a yoke 35 for connection of the teeth 34a, 34b, 34c, . . . are laminated and fixed, and it is attached to the rear side of the rotor 31. The permanent magnets 37a, 37b, 37c, . . . are attached to and constructed at a fixing portion 38 so that they face the armature core 33 and they are positioned so as to have different polarities to each other.
In such a construction, if electric current is caused to flow in the armature winding 36 of the linear motor 30, the rotor is caused to move in the axial direction by an electromagnetic action between the armature winding 36 and permanent magnets 37a, 37b, 37c, . . . . 
However, there are the following problems in a prior art problems.
(1) Since the teeth 34a, 34b, 34c, . . . to form a winding accommodation groove and a yoke 35 to connect the teeth 34a, 34b, 34c, . . . were integrally punched out like comb teeth to compose an armature core, the length of the armature core in the axial direction as a block becomes longer, wherein it was not possible to adequately set the length of the linear motor in the axial direction.
(2) Since the teeth 34a, 34b, 34c, . . . and yoke 35 are integrally punched out, a magnetic flux from the armature winding is, as shown by dotted lines in FIG. 9, spread from the teeth 34a of the armature core 33 to the permanent magnet 37a, and a magnetic circuit in which the magnet flux passed through the permanent magnet 37a passed from the teeth 34b through the yoke 35 via the adjacent permanent magnet 37b, wherein since the flowing direction of the magnet flux in the teeth differs from that in the yoke, it was necessary to use an armature core 33 not having any directivity. Therefore, there was a shortcoming due to which the magnetic permeability was lowered, and the peak thrust was decreased.
(3) Also, FIG. 10 shows one example of winding patterns of a moving coil type linear motor. Where it is assumed that, in the armature core on which an armature coil is wound, the number of phases is n, the number of permanent magnets is p, and the number of teeth facing one polarity is q, the number N of teeth to be provided in the armature core is N=nxc3x97pxc3x97q, and in the armature core equidistantly provided with the number of teeth, three-phased windings U, V and W of the armature winding are wound so as to secure the teeth pitch equivalent to two or more pitches by skipping coils. However, the magnetic circuit of the moving armature cores is not made endless, but is opened at both ends. Therefore, an edge effect occurs, a cogging thrust Tc of one cycle is produced by a change in the magnetic resistance resulting from the core edge part in a magnetic polarity pitch of a field system magnet, whereby a problem of production unevenness in the thrust occurs when the armature and field system relatively move.
The present invention was developed to solve the abovementioned problems and shortcomings, and it is therefore an object of the invention to provide a linear motor which is capable of increasing the peak thrust and simultaneously counterbalancing a cogging thrust produced due to an edge affect of an armature, and in which the length of the linear motor in the axial direction can be adequately constructed.
In order to solve the abovementioned problems, a linear motor according to the first aspect of the invention having a field system yoke in which a plurality of permanent magnets having alternatively different polarities are placed adjacent to each other, and an armature having an armature winding wound on an armature core facing the permanent magnet row via a magnetized space, in which any one of the field system yoke and the armature is made into a stator, and the other is made into a rotor, and the field system yoke and the armature are caused to relatively run, wherein the armature core has a winding accommodation groove, and a convex and concave engagement part, which are formed on both sides of an armature iron plate by punching out electromagnetic steel plate so as to become roughly rectangular, the armature iron plate is laminated to constitute a core block, and the armature winds the armature winding in order in the winding accommodation groove of the respective core blocks, and at the same time, a plurality of engagement portions are engaged with each other.
A linear motor according to the second aspect of the invention is featured in that, in addition to the linear motor as set forth in the first aspect, the lengthwise direction orthogonal to the permanent magnet row in the respective core blocks is the same as the rolling direction of the electromagnetic steel plate.
A linear motor according to the third aspect of the invention is featured in that, in addition to the linear motor as set forth in the second aspect, the electromagnetic steel plate is made of an oriented electromagnetic steel plate.
A linear motor according to the fourth aspect of the invention is featured in that, in the linear motor as set forth in any one of the first through the third aspects, an armature core which accommodates the armature winding and has a plurality of core blocks engaged therein is made into a first core block group, a second core block being a dummy, which has a space provided therein and does not accommodate an armature winding, is provided at at least one end of both ends in the direction of the permanent magnet row of the first core block group, and the second core block has the same shape as that of the respective core blocks which constitute the first core block group.
A linear motor according to the fifth aspect of the invention is featured in that, in addition to any one of the first through the fourth aspects, the interval between the first core block group and the second core block is set to one-second of the pitch of the permanent magnet.
A linear motor according to the sixth aspect of the invention is featured in that, in addition to any one of the first through the fourth aspects, the second core block is provided at both sides of the first core block group, and at the same time, the interval between the first core block group and the second core block is set to two-thirds or one-third of the pitch of the permanent magnet.